What if Susan wasn't the oldest daughter? What if one of the Pevensie had magic before they entered Narnia?

I was raised killing, torturing, fighting. My Mother, the White Witch, told me to never have mercy. Well I have never EVER broken that rule, until the prophecy started becoming true. Only then did my ice cold heart melt, when i met one of the rightful kings of Narnia. *Credits to the Movie* (Edmund Fanfiction)